When using a growler, what indicates that a short exists between an armature segment?

A growler is a device used to diagnose short circuits on the armature of a DC electric motor or generator. When a short exists between an armature segment, it creates an irregular magnetic field as the growler is applied. This irregularity leads to a situation where the magnetic forces acting on the armature are uneven, causing the blade held over the armature to begin to vibrate and exhibit a "chattering" motion.

The vibration and chattering indicate that the magnetic fields generated are not balanced due to the short circuit, thus providing a clear signal to the technician that a problem exists. This behavior is characteristic of a fault, as the continuous disturbance of the magnetic field directly relates to the electrical fault within the armature segments.

Other methods or outcomes, such as a loud sound from the armature or abnormal spinning speeds, do not directly indicate a short circuit to the same extent or clarity as the vibration and chattering do. This makes the detection of vibration and chattering over the armature a more reliable and clear indication of an existing short circuit.